1. Field of the Invention
The present invention relates to a display control apparatus which includes a flat panel display unit (FPD) such as a plasma display unit as a standard I/O device and can be arbitrarily connected to a CRT display unit, and can be suitable for use in a computer system such as a personal computer and a personal workstation.
2. Description of the Related Art
Liquid crystal displays and plasma displays have been used as display units for conventional lap-top type personal computers and personal workstations. However, strong demand has arisen for running an application program created for a Cathode Ray Tube (CRT) display unit in the above computer so as to utilize a wealth of all previous software. For this reason, the above computer equipped with a plasma display unit as a standard Input/Output (I/O) device is arranged to be connectable to a CRT display unit as an optional I/O device.
The plasma and CRT display units, however, have different display timing data. For example, the CRT display unit has a horizontal resolution of 720 dots (standard text display), while the plasma display unit has a horizontal resolution of 640 dots. It is impossible for the plasma display unit to use and execute a basic input and output system program (BIOS) for CRT display units and application programs without modifications.
For this reason, a conventional computer system cannot simultaneously operate CRT and plasma display units (this mode of operation is hereinafter referred to as a dual display mode) by using a CRT display unit application program.